These authors conclude that M98K has a modifier effect and is not a risk factor for primary open-angle glaucoma (POAG) by itself.
French POAG cases, case+: 11, case-: 226. French controls, cont+: 5, cont-: 105. Moroccan POAG cases, case+: 6, case-: 50, Moroccan controls: cont+: 5, cont-: 55. These numbers indicate no increased incidence of this variant in POAG cases for either French, Moroccan, or combined groups.
They observe lower intraocular pressure in M98K carriers and hypothesize that M98K could be a modifier of the intraocular pressure — not necessarily increasing the risk of disease, but what might be considered normal intraocular pressure in noncarriers could be unusually high & pathogenic for an M98K carrier.